Association between aspartate aminotransferase-to-alanine aminotransferase ratio and insulin resistance among US adults.

OBJECTIVE To determine whether a low aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio (AST/ALT ratio) is associated with insulin resistance among those without liver dysfunction. METHODS In this cross-sectional study of the National Health and Nutrition Examination Survey (NHANES) 2011-2016, we included 2747 (1434 male and 1313 nonpregnant female) adults ≥20 years without evidence of liver dysfunction (ALT<30 in male and <19 in female, negative viral serologies, no excess alcohol consumption, no elevated transferrin saturation, AST/ALT <2). Serum AST/ALT ratio was categorized into sex-specific quartiles (female: <1.12, 1.12-1.29, 1.29-1.47, ≥1.47 and male: <0.93, 0.93-1.09, 1.09-1.26, ≥1.26). The primary outcome was insulin resistance, as determined by Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) index score ≥3. Covariate-adjusted odds ratios (ORs) were estimated. Study analysis completed from 13 March 2020 to 21 April 2021. RESULTS Among the 2747 individuals, 33% had insulin resistance. Those in the lowest quartile (Q1) of AST/ALT had 75% higher adjusted odds of insulin resistance compared to the highest quartile (Q4) [aOR (95% confidence interval (CI), 1.75 (1.20-2.57)]. This association was more pronounced in those with elevated BMI [Q1 vs. Q4; BMI ≥ 25: 2.29 (1.58-3.33), BMI < 25: 0.66 (0.26-1.69); NAFLD per Fatty Liver Index ≥ 60: 2.04 (1.21-3.44), No NAFLD: 1.68 (0.94-3.01)]. CONCLUSION Lower AST/ALT ratio is associated with increased insulin resistance among those with healthy-range ALT, especially in those with BMI greater than or equal to 25 kg/m2.